This invention relates to display devices for displaying a singe image or a series of images represented by an electrical signal commonly known as a video signal.
Such a device may be used in a television system, particularly for projecting televised images onto a large screen.
It is known that a cathode ray tube may be used for displaying an image, but such a tube wastes a large volume of space for displaying such a flat image.
Accordingly, numerous devices have been proposed to replace cathode ray tubes, but the results have always been disappointing. In some cases, the structure is complicated and brilliance is poor, as in the case of plasma screens such as that described by Yoshifumi Amano in the Journal "IEEE Transactions on Electron Devices", Vol. ED-22, No. 1, January, 1975. In other cases, the response time is slow thereby precluding use in a television system, as in the case of the numerous liquid-crystal devices with which experiments have hitherto been conducted.
French Pat. No. 2,275,087 granted to the Applicants herein on Feb. 13, 1976 on the basis of an application filed on June 14, 1974, describes a display arrangement which utilizes a thermo-electric effect in a liquid crystal layer, the image being recorded by scanning the layer with an infrared beam produced by a laser and deflected by electro-optical or acousto-optical deflectors.
This light source and these deflectors are both unwieldy to use and expensive to produce. However, the most serious disadvantage is that the scan used has to be slow enough to allow a local dot-by-dot phase change of the liquid crystal layer in response to the heat supplied by the infrared beam. A thermal phenomenon used in this manner is too slow to enable the arrangement to be utilized in a television system.